A liquid crystal display having color filters with recess structures

ABSTRACT

A liquid crystal display includes a lower substrate, an upper substrate positioned parallel with the lower substrate, and a plurality of pixel units between the lower substrate and the upper substrate. Each pixel unit includes an upper transparent electrode, a liquid crystal layer, a lower transparent electrode, and a color filter with recess structures.

BACKGROUND OF INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a liquid crystal display (LCD),and more particularly, to an LCD comprising color filters with recessstructures.

[0003] 2. Description of the Prior Art

[0004] Due to low prices and high quality of liquid crystal displays(LCDs), the LCD is widely applied in notebooks, PDAs, mobile phones, andso on.

[0005] Please refer to FIG. 1. FIG. 1 shows a sectional view of aconventional color LCD 11. The color LCD 11 comprises a lower glasssubstrate 9, an upper glass substrate 2 positioned parallel to and abovethe lower glass substrate 9, and a plurality of pixel units (not shownin FIG. 1) positioned between the lower glass substrate 9 and the upperglass substrate 2, each of the pixel units including a red color filter3R, a green color filter 3G, or a blue color filter 3B. An inner surfaceof the upper glass substrate 2 includes an upper transparent electrode4, and an inner surface of the lower glass substrate 9 includes a lowertransparent electrode 8 and a plurality of thin film transistors (notshown in FIG. 1) for controlling the pixel units. Furthermore, a liquidcrystal layer 6 is positioned between the upper glass substrate 2 andthe lower glass substrate 9, and an exposed portion of an outer surfaceof the upper glass substrate 2 and an exposed portion of anouter surfaceof the lower glass substrate 9 respectively include an upper polarizer 1and a lower polarizer 10. The above-mentioned color LCD 11 is atransmissive color LCD. A reflective color LCD similar to thetransmissive color LCD further comprises a reflection layer (not shownin FIG. 1) positioned between the color filters 3R, 3G, 3B and the lowerglass substrate 9. Additionally, a transflective color LCD comprises adiffusion layer (not shown in FIG. 1) positioned between the upperpolarizer 1 and the lower polarizer 10.

[0006] Since the transmissive LCD is a passive luminous device, abacklight source (not shown in FIG. 1) positioned behind the lower glasssubstrate 9 is required for the color LCD 11. A white light is radiatedfrom the backlight source and passes through the color filters 3R, 3G,3B so as to enable each of the pixel units to respectively display a redlight, a green light, and a blue light. However, only portions of thewhite light with specific wavelengths can pass through the colorfilters. For the reflective color LCD, the white light radiated from thebacklight source has to pass through the color filters and reach asurface of the reflection layer, then the light is reflected by thereflection layer and again passes through the color filters forrespectively displaying a red light, a green light, and a blue light.Consequently, comparing to the transmissive color LCD, the colordeepness of the reflective color LCD is greater, and the problem of thereflective color LCD having insufficient brightness is more serious.

[0007] For solving the above-mentioned problems, a conventional colorLCD 15 comprises light transmitting holes 18 respectively formed in thecolor filters 16R, 16G, 16B of each pixel unit, as shown in FIG. 2.Therefore, the transmittance of the color filters 16R, 16G, 16B can beincreased for improving a brightness of a transmissive color LCD or areflective color LCD, and a color deepness of the transmissive color LCDor the reflective color LCD is also regulated. However, the method offorming holes 18 in the color filters 16R, 16G, 16B results in anon-uniform cell gap 19, and an overcoating layer 17 is required forcovering the color filters 16R, 16G, 16B. Because the gap 19 caused bythe formation of the holes 18 is great, the overcoating layer 17 formedfor planarization is not so effective, and a stability and a quality ofthe LCD 15 is reduced.

SUMMARY OF INVENTION

[0008] It is therefore an objective of the claimed invention toprovideanLCD comprising color filters with recess structures for solvingthe above-mentioned problems.

[0009] According to the claimed invention, a liquid crystal displaycomprises a lower substrate, an upper substrate positioned parallel withthe lower substrate, and a plurality of pixel units between the lowersubstrate and the upper substrate. Each pixel unit includes an uppertransparent electrode, a liquid crystal layer, a lower transparentelectrode, and a color filter with recess structures.

[0010] According to the claimed invention, a liquid crystal displaycomprises a lower substrate, an upper substrate positioned parallel withthe lower substrate, and a plurality of pixel units, each of the pixelunits including an upper transparent electrode, a liquid crystal layer,a lower transparent electrode, and a color filter and wherein each ofthe color filters includes both a first region and a second region, anda surface of the first region has a plurality of recess structures.

[0011] The color LCD provided by the claimed invention comprises colorfilters with recess structures. Consequently, the transmittance of thecolor filters can be effectively increased, which results in improving abrightness of the LCD. Also, the problem of a non-uniform cell gapcaused by forming holes in the color filters according to a conventionalmethod can be prevented. Additionally, the recess structures of thecolor filters are able to scatter light. Therefore, a diffusing layer ofa transflective LCD can be replaced by the color filters with recessstructures, and a cost of the transflective LCD is substantiallyreduced.

[0012] These and other objectives of the claimed invention will no doubtbecome obvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment, which isillustrated in the multiple figures and drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0013]FIG. 1 is a sectional view of a conventional color LCD.

[0014]FIG. 2 is a sectional view of a conventional color LCD comprisingcolor filters with hole structures.

[0015]FIG. 3 is a sectional view of a color LCD comprising color filterswith recess structures according to a first embodiment of the presentinvention.

[0016]FIG. 4 is a sectional view of a color LCD comprising color filterswith recess structures according to a second embodiment of the presentinvention.

[0017]FIG. 5 is a top view of each pixel unit of a transflective colorLCD according to a third embodiment of the present invention.

[0018]FIG. 6 is a top view of each pixel unit of a transflective colorLCD according to a fourth embodiment of the present invention.

DETAILED DESCRIPTION

[0019] First, a transmissive color LCD is provided as a first embodimentof the present invention, as shown in FIG. 3. Comparing to theconventional color LCD 11, the color LCD 31 of the present inventionalso comprises a lower glass substrate 29, an upper glass substrate 22positioned parallel to and above the lower glass substrate 29, aplurality of pixel units 25 positioned between the lower glass substrate29 and the upper glass substrate 22, and a plurality of thin filmtransistors (not shown in FIG. 3) positioned on a top surface of thelower glass substrate 29, which are used to control each of the pixelunits 25. Each of the pixel units 25 includes a red color filter 23R, agreen color filter 23G, or a blue color filter 23B, and an uppertransparent electrode 24, a liquid crystal layer 26, and a lowertransparent electrode 28. An exposed portion of an outer surface of theupper glass substrate 22 and an exposed portion of an outer surface ofthe lower glass substrate 29 respectively includes an upper polarizer 21and a lower polarizer 30.

[0020] The main difference between the color LCD 31 of the presentinvention and the conventional transmissive color LCD 11 is that thecolor LCD 31 uses a predetermined mask pattern design including aplurality of matrix or interlaced patterns to reduce a resolution of thepatterns and also uses the restriction of photo resist due to thereduced resolution to form a plurality of recess structures with eitheruniform size or non-uniform size on surfaces of the color filters 23R,23G, 23B during a development process. Therefore, the transmittance ofthe color filters 23R, 23G, 23B is increased, and the brightness of thecolor LCD 31 is effectively improved.

[0021] The present invention can also use the predertermined maskpattern design to form the recess structures only on portions of thesurfaces of the color filters 23R, 23G, 23B. The area of the portions ofsurfaces including the recess structure and the distribution density ofthe recess structures can be changed to regulate a brightness and colordeepness of the color LCD 31 so as to enable the LCD 31 to display adesired brightness and color deepness. In other words, when the area ofthe surfaces including the recess structures is greater, thetransmittance of the color filters is also greater, and the brightnessof the color LCD 31 is improved and the color of the color LCD 31 is notdeep. When the distribution density of the recess structures is greater,the transmittance of the color filters is also greater, the brightnessof the color LCD 31 is improved and the color of the color LCD 31 is notdeep.

[0022] Additionally, the color filters with recess structures of thepresent invention can also be applied to a reflective or a transflectivecolor LCD. A reflective color LCD 51 is provided as a second embodimentof the present invention, as shown in FIG. 4. The reflective color LCD51 comprises a lower glass substrate 49, an upper glass substrate 42positioned parallel to and above the lower glass substrate 49, and aplurality of pixel units 45 positioned between the lower glass substrate49 and the upper glass substrate 42. Each of the pixel units 45 includesa red color filter 43R, a green color filter 43G, or a blue color filter43B, and an upper transparent electrode 44, a liquid crystal layer 46, alower transparent electrode 48, and a reflection layer 47. An exposedportion of the surfaces of the upper glass substrate 42 and the lowerglass substrate 49 respectively includes an upper polarizer 41 and alower polarizer 50. The reflective color LCD 51 further comprises aplurality of thin film transistors (not shown in FIG. 4) for controllingthe pixel units 45. A plurality of recess structures are formed onsurfaces of the color filters so as to increase the transmittance of thecolor filters and further improve the brightness and regulate the colordeepness of the color LCD 51.

[0023] According to the second embodiment of the present invention, therecess structures are distributed completely on the surfaces of thecolor filters 43R, 43G, 43B. However, the recess structures can onlyformed on portions of the surfaces of the color filters 43R, 43G, 43B byusing a different mask pattern design. Consequently, the area of theportions of surfaces including the recess structure and the distributiondensity of the recess structures can be changed to regulate a brightnessand color deepness of the color LCD 51 so as to enable the LCD 51 todisplay a desired brightness and color deepness.

[0024] Finally, a transflective color LCD is provided as a thirdembodiment of the present invention. Each pixel unit of thetransflective color LCD, which is similar to the pixel unit of thereflective color LCD, comprises a color filter, an upper transparentelectrode, a liquid crystal layer, a lower transparent electrode, and areflection layer. The reflection layer further comprises an opening, andtherefore a transmissive region of the LCD is produced by the openingand a region of the color filter opposite to the opening of thereflection layer. Comparatively, because the reflection layer ispositioned under and outside of the transmissive region of the LCD, areflective region of the LCD is formed. Consequently, each pixel unitcan use ambient light passing through the reflective region of the colorfilter or use back light passing through the transmissive region of thecolor filter to display a red light, a green light, or a blue light.

[0025]FIG. 5 is a top view of each pixel unit 65 of a transflectivecolor LCD (not shown in FIG. 5) according to a third embodiment of thepresent invention. As shown in FIG. 5, the color filters 63R, 63G, 63Bof each pixel unit 65 respectively comprise a transmissive region 61 anda reflective region 62. A plurality of recess structures are formed bothon surfaces of the transmissive region 61 and the reflective region 62so as to improve brightness and regulate a color deepness of thetransflective color LCD. Furthermore, a diffusing layer (not shown inFIG. 5) is usually required for the transflective color LCD to increasean illumination cone. However, because the recess structures of thecolor filters 63R, 63G, 63B are able to scatter light, theabove-mentioned diffusing layer can be replaced by the color filters63R, 63G, 63B with recess structures, and a cost of the transflectiveLCD is substantially reduced.

[0026]FIG. 6 is a top view of each pixel unit 75 of a transflectivecolor LCD according to a fourth embodiment of the present invention. Asshown in FIG. 6, only surfaces of reflective regions 72 of the colorfilters 73R, 73G, 73B include a plurality of recess structures. When aconventional transflective color LCD displays an image, for each pixelunit, ambient light passes through the reflective region of the colorfilter twice, and backlight only passes through the transmissive regionof the color filter once, which results in poor brightness and a deepercolor deepness of the reflective region in the same pixel unit.Therefore, according to the fourth embodiment of the present invention,the recess structures are only formed on surfaces of reflective regions72 of the color filters 73R, 73G, 73B to regulate brightness and thecolor deepness. Consequently, a difference in brightness and colordeepness occurred between the reflective region 72 and the transmissiveregion 71 of the same pixel unit 75 can be reduced.

[0027] The color LCD provided by the present invention comprises colorfilters with recess structures. Consequently, the transmittance of thecolor filters can be effectively increased, which results in animprovement of brightness of the LCD, and a color deepness of the colorLCD can be regulated. Comparing to a prior art color LCD, the problem ofa non-uniform cell gap caused by forming holes in the color filters canbe prevented. For a transflective color LCD, the recess structures ofthe present invention can be formed only on surfaces of reflectiveregions of the color filters so as to reduce a difference in brightnessand color deepness occurred between the reflective region and thetransmissive region of the same pixel unit. Furthermore, because thecolor filters with recess structures are able to scatter light, adiffusing layer of the transflective LCD can be omitted, and a cost ofthe transflective LCD is substantially reduced.

[0028] Those skilled in the art will readily observe that numerousmodifications and alterations of the device may be made while retainingthe teaching of the invention. Accordingly, the above disclosure shouldbe construed as limited only by the metes and bounds of the appendedclaims.

What is claimed is:
 1. A liquid crystal display comprising: a lowersubstrate; an upper substrate positioned parallel with the lowersubstrate; and a plurality of pixel units, each of the pixel unitsincluding an upper transparent electrode, a liquid crystal layer, alower transparent electrode, and a color filter; wherein a surface ofeach color filter has a plurality of recess structures.
 2. The liquidcrystal display of claim 1 wherein a distribution density of the recessstructures is used to regulate brightness and a color deepness of theliquid crystal display.
 3. The liquid crystal display of claim 1 whereineach of the pixel units respectively comprises a reflection layerpositioned between the color filter and the lower substrate.
 4. Theliquid crystal display of claim 3 being a reflective liquid crystaldisplay.
 5. The liquid crystal display of claim 3 wherein each of thereflection layers includes an opening.
 6. The liquid crystal display ofclaim 5 being a semi-transmissive and semi-reflective liquid crystaldisplay.
 7. The liquid crystal display of claim 1 further comprising aplurality of thin film transistors for respectively controlling each ofthe pixel units.
 8. A liquid crystal display comprising: a lowersubstrate; an upper substrate positioned parallel with the lowersubstrate; and a plurality of pixel units, each of the pixel unitsincluding an upper transparent electrode, a liquid crystal layer, alower transparent electrode, and a color filter; wherein each of thecolor filters includes both a first region and a second region, and asurface of the first region has a plurality of recess structures.
 9. Theliquid crystal display of claim 8 wherein an area of the first region ofthe color filter is used to regulate brightness and a color deepness ofthe liquid crystal display.
 10. The liquid crystal display of claim 8wherein a distribution density of the recess structures is used toregulate brightness and a color deepness of the liquid crystal display.11. The liquid crystal display of claim 8 wherein each of the pixelunits respectively comprises a reflection layer positioned between thecolor filter and the lower substrate.
 12. The liquid crystal display ofclaim 11 being a reflective liquid crystal display.
 13. The liquidcrystal display of claim 11 wherein each of the reflection layersrespectively includes an opening opposite to the second region of eachcolor filter.
 14. The liquid crystal display of claim 13 being asemi-transmissive and semi-reflective liquid crystal display.
 15. Theliquid crystal display of claim 8 further comprising a plurality of thinfilm transistors for respectively controlling each of the pixel units.